Optimised heat exchange system of a turbomachine

ABSTRACT

A heat exchange system of a turbomachine, includes a heat exchanger including a support wall, a plurality of fins each extending in a radial direction from a radially outer surface of the support wall, and a cover covering the fins, wherein the cover is connected, upstream in the direction of flow of the air flow, to a first profiled wall, and downstream to a second profiled wall, the first profiled wall being arranged upstream from the fins and configured to guide and slow down the flow of air entering the heat exchanger through the fins, and the second profiled wall being arranged downstream from the fins and configured so as to accelerate the flow of air leaving the heat exchanger, wherein the cover has an at least partially curvilinear aerodynamic profile and an outer peripheral surface having surface continuity with radially outer surfaces of the first and second walls.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the general field of aeronautic. Itaims in particular at a heat exchange system for a turbomachine.

BACKGROUND

A turbomachine, in particular of an aircraft, comprises various membersand/or equipment that need to be lubricated and/or cooled, such asrolling bearings and gears. The heat released by these components, whichcan be very high depending on the power of the member and/or theequipment, is transported by a fluid and evacuated towards cold sourcesavailable in the aircraft.

It is known to equip the turbomachine with one or more heat exchangesystems to carry out the heat exchange between the fluid (typically oil)and the cold source (air, fuel, etc.). There are even different types ofheat exchange systems, such as for example the fuel/oil heat exchangers,generally known by the acronym FCOC (Fuel Cooled Oil Cooler) and theair/oil heat exchangers, known by the acronym ACOC (Air-Cooled OilCooler). Examples of heat exchanger systems are known from the documentsEP-A2-1916399, CN-A-109210961, WO-A1-2008/025136, and U.S. Pat. No.4,254,618.

The FCOC heat exchangers have a dual function of heating the fuel beforethe combustion in the combustion chamber of the turbomachine and coolingthe oil heated by the heat dissipations of the turbomachine. However,the FCOC heat exchangers are not sufficient to absorb all the heatdissipations because the temperature of the fuel is limited for safetyreasons.

The additional cooling is obtained by the ACOC heat exchangers, inparticular those of the surface type known by the acronym SACOC. Thesurface heat exchangers are usually located in the secondary vein of theturbomachine and use the secondary air flow to cool the oil circulatingin the turbomachine. These heat exchangers are in the form of a metallicsurface piece allowing the passage of oil in machined channels. Thesecondary air flow is guided along fins carried by this surface pieceand which have the role of increasing the contact surface with thesecondary air flow and extracting the calories. However, thedisadvantage of the SACOC heat exchangers is that they create additionalpressure drops in the relevant secondary vein, since they disturb theair flow, which has an impact on the performance of the turbomachine aswell as on the specific fuel consumption.

Their aerothermal performance (ratio between the thermal powerdissipated and the pressure drop induced on the side of the secondaryair flow) is low.

In addition, the cooling requirements of the lubricating fluid areincreasing due to the higher rotation speeds and the power requirementsto meet the specification trends on the turbomachines.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a heat exchangesystem allowing to optimize the efficiency of the heat exchanges bycontrolling the flow rate of the air flow passing through the system,while avoiding the pressure drops and disturbing as little as possiblethe air flow, in particular the secondary air flow of a turbomachinewith which it cooperates.

This is achieved in accordance with the invention by a turbomachine heatexchange system comprising a heat exchanger comprising a support wall, aplurality of fins each extending in a radial direction from a radiallyouter surface of the support wall and intended to be swept by an airflow, and a cover covering the fins, the cover being connected upstream,in the direction of flow of the air flow, to a first profiled wall anddownstream to a second profiled wall, the first profiled wall beingarranged upstream from the fins and configured so as to guide and slowdown the air flow entering the heat exchanger through the fins, and thesecond profiled wall being arranged downstream of the fins andconfigured so as to accelerate the air flow exiting the heat exchanger,the cover having an at least partly curvilinear aerodynamic profile andan outer peripheral surface having surface continuity with radiallyouter surfaces of the first and second walls.

Thus, this solution allows to achieve the above-mentioned objective. Inparticular, by modifying the flow conditions in the heat exchanger, aheat dissipation with an optimal aerothermal performance is ensured,which contributes to the reduction of the pressure drops. In fact, whenthis heat exchange system is installed in a turbomachine and inparticular in a secondary vein, the flow of the secondary air flow isvery turbulent, which corresponds to a high flow Reynolds number thatdegrades the aerothermal performance of the heat exchanger. The flowreaches Mach values of about 0.6 at take-off and cruise. By slowing downthe flow velocity of the air flow at the inlet of this heat exchanger(without modifying its intrinsic configuration) and by increasing thevelocity at the outlet, it allows to optimize its aerothermalperformance and thus minimize the pressure drops for a given heatdissipation. Furthermore, the first and second profiled walls allow tobetter control and improve the aerodynamics of the part of the air flowthat bypasses the exchanger of the fins, i.e. that does not pass throughthe fins. The cover with its aerodynamic profile allows the heatexchanger to be better integrated into the air flow, in particular thesecondary air flow.

The heat exchange system also comprises one or more of the followingcharacteristics, taken alone or in combination:

-   -   each first and second profiled walls is attached to the support        wall via support elements extending radially from the radially        outer surface.    -   the first profiled wall comprises a first wall portion forming,        with the support wall, an air inlet having a first radial        height, and the second profiled wall comprises a first wall        portion forming, with the support wall, an air outlet having a        second radial height, the ratio between the first height and the        second height being equal to or greater than 0.5.    -   the cover comprises a first wall portion defined in an inclined        plane forming a predetermined angle with a plane in which the        radially outer surface of the support wall is defined.    -   the cover has a second wall portion which is curvilinear and        arranged upstream of the first portion.    -   the heat exchanger comprises a profiled panel covering the fins,        which is substantially flat or curved and extends radially        between the fins and the cover.    -   the profiled panel extends to a maximum radial distance from the        radially outer surface which is greater than the first height        and the second height respectively of the first and second        profiled walls.    -   the exchange system comprises a fluid circulation circuit in        which a fluid intended to cool and/or lubricate members and/or        equipment of the turbomachine circulates, the circuit comprising        a first duct arranged in the support wall and a second duct        arranged in the profiled panel.    -   the fluid circulation circuit comprises two channels connecting        the first and second ducts to each other.    -   the second curvilinear wall portion has a radius of curvature.    -   the radius of curvature is a function of the length of the        profiled panel in a longitudinal direction perpendicular to the        radial direction, the ratio between the length of the profiled        panel and the radius of curvature being between 0.5 and 1.5 mm.    -   the fins are continuous and rectilinear each along a        longitudinal direction or are discontinuous and arranged in        staggered or are corrugated.    -   at least one fin has different heights in the radial direction        and varies so as to conform the profile of the cover.    -   the fins comprise a first type of fins and a second type of fins        arranged on the radially outer surface along a transverse        direction perpendicular to the radial direction, the fins of the        first type of fins each extending radially between the support        wall and the cover, and each being attached to the cover so as        to bear the cover over their full radial heights.    -   the fins are arranged transversely so that every third fin is a        fin of the first type.    -   the fins of the first type have a central portion with a radial        height less than or equal to the height of the cover.    -   the heat exchanger is made by additive manufacturing.    -   the panel and the first and second profiled walls are made in        one piece.    -   the cover and the panel are made in one piece.    -   the fins are attached to the panel.    -   the fins are made in one piece with the panel.    -   the heat exchange system is intended to be arranged in a        secondary vein of the turbomachine.    -   the heat exchanger is of the air/fluid type and preferably a        surface heat exchanger.    -   the fluid is a lubricating oil.    -   the support elements are arranged and evenly distributed in a        transverse direction perpendicular to the longitudinal        direction.

The invention also relates to a turbomachine module with a longitudinalaxis X comprising an annular casing around the longitudinal axis inwhich an air flow circulates and a heat exchange system having any ofthe preceding characteristics which is arranged in the annular casing,the annular casing comprising an annular wall which guides at leastpartly the air flow and which has an opening or a recess in which theheat exchanger with the profiled panel or the cover is installed, thefirst wall being connected upstream of the profiled panel or the coverto a portion of the annular wall and the second wall being connecteddownstream of the profiled panel or the cover to a portion of theannular wall.

The heat exchanger is buried in the wall of the annular casing.

The invention further relates to a turbomachine comprising at least oneheat exchange system having any of the foregoing characteristics and/ora turbomachine module as aforesaid.

BRIEF DESCRIPTION OF FIGURES

The invention will be better understood, and other purposes, details,characteristics and advantages thereof will become clearer upon readingthe following detailed explanatory description of embodiments of theinvention given as purely illustrative and non-limiting examples, withreference to the appended schematic drawings in which:

FIG. 1 is an axial cross-sectional view of an example of a turbomachineto which the invention applies;

FIG. 2 is a perspective and partial view of a heat exchange systemintended to equip a turbomachine according to the invention;

FIG. 3 is a schematic view in axial section of an example of a heatexchange system according to the invention;

FIG. 4 is a perspective view of an embodiment of a heat exchange systemaccording to the invention;

FIG. 5 illustrates schematically and in axial cross-section a variant ofthe heat exchange system shown in FIG. 4;

FIG. 6 is a perspective view of another embodiment of the heat exchangesystem according to FIG. 4;

FIG. 7 represents an example of heat exchange system with a fluid ductarranged in one of the walls covering the fins according to theinvention;

FIG. 8 illustrates according to a perspective and skinned view anexample of fin arrangement of a heat exchanger of a heat exchange systemcooperating with a fluid circulation circuit according to the invention;

FIG. 9 shows in perspective another embodiment of a heat exchange systemwith a cover according to the invention;

FIG. 10 is an axial cross-sectional view of the embodiment according toFIG. 9;

FIG. 11 is a schematic side view of another embodiment of a heatexchange system with a heat exchanger the fins of which have differentheights;

FIG. 12 shows in perspective and partially another embodiment of a heatexchanger of an exchange system, the heat exchanger comprising a covercovering fins according to the invention;

FIG. 13 is a perspective view of the heat exchanger of FIG. 12 withoutits cover according to the invention;

FIG. 14 is a schematic view in axial section of another embodimentwherein a heat exchanger is buried in a wall of the turbomachineaccording to the invention;

FIG. 15 is another schematic view in axial section of another embodimentof a heat exchanger buried in a wall of the turbomachine according tothe invention;

FIG. 16 is a schematic view in axial section of another embodiment of aheat exchanger buried in a wall of the turbomachine according to theinvention; and

FIG. 17 is a schematic and axial cross-sectional view of anotherembodiment of a heat exchanger buried in a wall of the turbomachineaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an axial cross-sectional view of a turbomachine oflongitudinal axis X to which the invention applies. The turbomachineshown is a double-flow turbomachine 1 intended to be mounted on anaircraft. Of course, the invention is not limited to this type ofturbomachine.

This double-flow turbomachine 1 generally comprises a gas generator 2upstream of which is mounted a fan or fan module 3.

In the present invention, the terms “upstream” and “downstream” aredefined in relation to the flow of gases in the turbomachine and herealong the longitudinal axis X.

The gas generator 2 comprises a gas compressor assembly (here comprisinga low pressure compressor 4 a and a high pressure compressor 4 b), acombustion chamber 5 and a turbine assembly (here comprising a highpressure turbine 6 a and a low pressure turbine 6 b). Typically theturbomachine comprises a low pressure shaft 7 which connects the lowpressure compressor and the low pressure turbine to form a low pressurebody and a high pressure shaft 8 which connects the high pressurecompressor and the high pressure turbine to form a high pressure body.The low-pressure shaft 7, centered on the longitudinal axis, drives herea fan shaft 9 by means of a gearbox 10. Rotational guide bearings 15 arealso allows to guide the low pressure shaft 7 in rotation with respectto a stationary structure of the turbomachine.

The fan 3 is shrouded by a fan casing 11 carried by a nacelle 12 andgenerates a primary air flow which circulates through the gas generator2 in a primary vein V1 and a secondary air flow which circulates in asecondary vein V2 around the gas generator 2. The secondary air flow isejected by a secondary nozzle 13 terminating the nacelle while theprimary air flow is ejected outside the turbomachine via an ejectionnozzle 14 located downstream of the gas generator 2. In the following,the fan casing and the nacelle are considered as one piece.

The guide bearings 15 and the speed reducer 10 in this example ofconfiguration of the turbomachine must be lubricated and/or cooled toensure the performance of the turbomachine. The power generated by theseis dissipated in a fluid from a fluid supply source installed in theturbomachine, which allows to lubricate and/or cool various membersand/or equipment of the turbomachine. Of course, other equipment of theturbomachine generates a lot of heat that must be extracted from itsenvironment.

To this end, the turbomachine comprises a heat exchange system 20 whichallows to cool the fluid intended to lubricate and/or cool these membersand/or equipment. In the present example, the fluid is an oil and thecold source intended to cool the oil is the air flow circulating in theturbomachine, in particular the secondary air flow.

The heat exchange system comprises a heat exchanger 21 which is arrangedin the fan casing of the turbomachine as schematically shown in FIG. 1.The heat exchanger is of the air/oil surface type.

With reference to FIG. 2, the heat exchanger 21 comprises a support wall22 which extends along a longitudinal direction L. The support wallextends here substantially flat. This wall may not be completely flatbut curved to follow the profile of the wall of the fan casing which isintended to carry the heat exchanger and which is substantiallycylindrical (of longitudinal axis X). The heat exchanger may occupy theentire wall of the fan casing or be arranged on a portion thereof.

The heat exchanger 21 also comprises a plurality of fins 23, each ofwhich rises here from a radially outer surface 24 of the support wall 22along a radial direction R. We use the term “direction” to describe theheat exchanger in particular. These fins are intended to be swept by thesecondary air flow entering the fan casing 11.

As can be seen in FIG. 2, the fins 23 are straight and each extend inthe longitudinal direction L (parallel to the circulation or flow of theair flow in the turbomachine and in particular in the heat exchanger).The longitudinal direction is parallel to the longitudinal axis in theinstallation situation. More precisely, each fin is flat. The fins arearranged successively and regularly on the radially outer surface alonga transverse direction T which is perpendicular to the longitudinaldirection L. They are still substantially parallel to one another. Eachfin has a leading edge BA and a trailing edge BF which are opposite toeach other in the direction of the air flow (see FIG. 3). Alternatively,the fins may be discontinuous and arranged in staggered and/orcorrugated in the radial or longitudinal direction.

In FIGS. 2 and 3, the heat exchanger 21 comprises a first profiled wall25 arranged upstream of the fins (along the direction of the air flowalong the radially outer surface) and which is configured to direct andguide the flow entering the heat exchanger. This first wall 25 is alsoconfigured to slow the air flow entering the heat exchanger. It has adivergent profile. The first wall 25 extends over a distance I1 at leastequal to the distance over which the fins are arranged. In particular,the width I1 of the first profiled wall 25 is greater than the widthover which the fins are arranged (in the transverse direction T).

The heat exchanger 21 is also provided with a second profiled wall 26arranged downstream of the fins so as to reduce the recirculationphenomena which occur downstream of the fins. The second profiled wallis also configured to accelerate the flow at the outlet of the heatexchanger.

In particular, in FIG. 3, each first and second profiled walls 25, 26has a substantially corrugated or curved shape in a plane RL (formed bythe perpendicular longitudinal L and radial R directions) perpendicularto the plane LT of the support wall 22. More specifically, the firstwall 25 comprises a first wall portion 25 a, upstream, forming with thesupport wall 22 an air inlet that has a first predetermined height healong the radial direction. The first height he is less than the radialheight hi of the fins. The first wall 25 comprises a second wall portion25 b (downstream of the first wall portion 25 a), which covers at leasta part of the fins (along the longitudinal direction L). The wallportion 25 b extends over an overlap distance re so as to better controland improve the aerodynamics of the air flow passing radially above(outside) the fins 23 according to FIG. 3. This second wall portion 25covers the leading edges BA of all the fins 23 aligned along thetransverse direction T.

The second wall 26 has substantially the same configuration as that ofthe first wall 25. However, it has a convergent profile. Its width 11 isidentical to that of the first wall 25. The second wall 26 alsocomprises a downstream wall portion 26 a forming an air outlet with thesupport wall 22, which has a second predetermined height hs along theradial direction. The second height hs is less than the height hi of thefins.

In the present embodiment, the ratio between the first height he and thesecond height hs is between 0.5 and 1.

Similarly, the second wall 26 comprises a second wall portion 26 b thatcovers at least a part of the fins 23 (along the longitudinal directionL). The second wall portion 26 b extends over an overlap distance rs forthe same purpose of controlling and improving the aerodynamics of theair flow passing over the heat exchanger. This second wall portion 25covers the trailing edges BF of all the fins 23 aligned along thetransverse direction T.

With reference to FIG. 3, the heat exchanger 21 comprises a plurality ofsupport elements 27 allowing to attach the fins to the support wall 22.In other words, the support elements 27 extend in the radial directionfrom the radially outer surface 24 of the support wall 22. The supportelements 27 are evenly distributed along the first and second walls 25,26 respectively. These ensure a better mechanical strength of the firstand second walls.

According to an alternative embodiment, the support elements 27 areconfigured to straighten the air flow entering the heat exchangerthrough the first profiled wall. Each support element 27 is in thepresent example attached to a central wall portion 25 c, 26 crespectively of the first and second walls. The central wall portions 25c, 26 c each have an inclination with respect to the longitudinaldirection. For this purpose, each support element 27 has a trapezoidalshape here.

The support elements 27 arranged at the inlet of the heat exchanger arepotentially thicker than the fins 23 for a better mechanical strength ofthe first wall 25 on the support wall 22. Indeed, the applied forces arepotentially more important locally, because of the gyration of the flowof the air flow upstream and its straightening by these same supportelements. In addition, these thicker support elements 27 are spacedfurther apart along the transverse direction to reduce the associatedpressure drops in this area where the heat exchanges are not optimal(higher flow velocity).

Alternatively, the support elements 27 and the fins 23 have the samethickness.

FIGS. 4 and 5 show another embodiment of the invention. The sameelements of the previous embodiment are represented by the samenumerical references. As illustrated, the heat exchanger 21 comprises aprofiled panel 28 covering the fins 23 so as to control the flow of theair flow within the heat exchanger without risk of bypassing the airflow through the heat exchanger. The fins 23 are thus arranged radiallybetween the support wall 22 and the profiled panel 28. The air flowentering the secondary vein V2 is separated into an air flow part F1that bypasses the heat exchanger and an air flow part F2 that flowsthrough the fins.

In this example of embodiment, the panel 28 extends along thelongitudinal direction L between the first wall 25 and the second wall26 and also has a width identical to that of the first and second walls25, 26. The panel 28 is substantially circular or curved (around thelongitudinal axis X in the situation of installation in theturbomachine). In particular, the panel comprises a first longitudinaledge 28 a that joins a first longitudinal end 25 d of the first profiledwall and a second longitudinal edge 28 b that joins a first end 26 d ofthe second wall 26 (FIG. 6). As illustrated in FIG. 5, the outerperipheral surface 29 of the panel 28 has a surface continuity with theradially outer surfaces 42, 43 of the first and second walls 25, 26.

The walls 25, 26 and the panel 28 are advantageously made in one pieceand for example by an additive manufacturing method (or 3D printing)such as a laser fusion method on powder bed.

The panel 28 extends at a radial distance equal to or greater than thatof the fins 23. In other words, this radial distance is greater than thefirst and second height he, hs of the first and second walls 25, 26.Advantageously, but not restrictively, the fins are attached, forexample by brazing, to the panel 28 and/or to the support wall 22.Alternatively, the fins 23 and the support wall 22 are formed in onepiece (i.e. from one material and in one piece) and advantageously byadditive manufacturing. Similarly, the fins and the panel 28 can be madein one piece. The additive manufacturing is carried out in a directionFA shown in FIG. 5 from upstream to downstream of the heat exchanger. Inthis case, to facilitate the additive manufacturing and in particularwithout support, the leading edge BA of the fins 23 has an angle alpha(α) with the radial direction.

Of course, the heat exchanger as a whole can be manufactured by anothermanufacturing method such as the forging.

Moreover, the fact of arranging the panel 28 on the fins allows toimprove the mechanical strength of the heat exchanger and thus to reducethe thickness of the fins 23. However, a thickness reduction of the fins23 also allows to reduce the mass of the heat exchanger 21. Similarly,in the case of support elements 27 which are thicker than the fins, andwhich are arranged with larger gaps between them along the transversedirection T, these may serve as a support for the panel 28 in flowoutlet area of the air flow.

According to an alternative of the previous embodiment and illustratedin FIG. 6, the heat exchanger 21 has a plurality of fins 23 which arearranged in a staggered manner on the radially outer surface 24 of thesupport wall 23 and along the direction of flow of the air flow F. Thereare rows of fins 23 in the direction of the longitudinal direction andin the direction of the transverse direction T. As in the previousembodiment, the fins are covered by a central profiled panel 28 which isextended upstream by the first wall 25 and downstream by the second wall26. The fins arranged in this way allow to intensify by interruption andredevelopment of the thermal boundary layers, which allows tosignificantly reduce the exchange surface for a given dissipated poweror to increase the power that can be dissipated in a given cluttering.

According to another embodiment represented in FIGS. 7 to 9, the heatexchange system comprises a fluid circulation circuit in whichcirculates a fluid intended to cool and/or lubricate members and/orequipment of the turbomachine. Typically, the fluidic circulationcircuit, using oil, is connected on the one hand to a supply source suchas a reservoir and on the other hand to one or more pumps designed topromote the delivery of the oil to the members and/or equipment.

In the present example, the fluid circulation circuit comprises a firstduct 30 which is arranged in the support wall 22 and on the side of aradially inner surface thereof. This radially inner surface is radiallyopposite the radially outer surface 24. The first duct 30 has an oilinlet and an oil outlet (not shown). Furthermore, the first duct 30 isin the form of a first pipeline 31 a and a second pipeline 31 b eachextending in the transverse direction and parallel to each other. Thefirst pipeline 31 a comprises the oil inlet while the second pipeline 31b comprises the oil outlet, the inlet and the outlet being placed nextto each other.

The fluid circulation circuit also comprises a second duct 32 which isarranged in the wall of the profiled panel 28. In other words, oilcirculates on both sides of the fins along the radial direction, whichallows to increase the convective exchanges and therefore the powerdissipated from the hot fluid (here oil) to the cold source (the airflow in the secondary vein). Advantageously, the second duct 32 ishollowed or formed in the material. As can be seen in FIG. 7, the panelcomprises a double wall which we refer to as first partition and secondpartition and which are radially spaced apart from each other to thenform the second duct 32. The latter has a cross-section shaped like a U(in the plane LT) which occupies substantially the entire area of thepanel 28. A strand 33 extending along the transversal direction risesradially into the duct 32 to form the two branches of the U. The strand33 has a width less than that of the panel 28 itself (along thetransverse direction T).

In FIG. 8, the fluid circulation circuit further comprises two channels34 a, 34 b which connect the first duct 30 and the second duct 32 toeach other. The channels 34 a, 34 b are arranged radially between thewall of the support 22 and the panel 28. A first channel 34 a opens oneither side (at the level of an end 35) into the first pipeline 31 a and(at the level of a first apex 36 of the branch of the U) into the secondduct. As for the second channel 31 b, it also opens on both sides (atthe level of an end 37) into the second pipeline 31 b and (at the levelof a second apex 38 of the branch of the U) into the second duct.

The channels 34 a, 34 b are advantageously formed in a partition 39which connects the panel 28 to the support wall 22. In this way, the“hot” oil enters through the inlet of the first pipeline 31 a, into thesecond duct 32 via the first channel 34 a, circulates around the secondduct, then through the second channel 34 b to circulate in the secondpipeline 31 b and finally exits through the oil outlet as a “cold” oil.The performance of the heat exchanger is thus improved because thetemperature of the fins will increase and be more uniform on theirsurfaces, thus favoring the propagation of the heat by conduction.

Alternatively, each first duct 30 and second duct 32 may beindependently connected to the supply source. In this case, weunderstand that each of the first and second ducts 30, 32 comprises anoil inlet and outlet respectively. The heat exchanger has no channels 34a, 34 b.

The fins 23 which are shown in this embodiment (FIG. 8) arediscontinuous (staggered pitch) i.e. there are several fins in a row offins substantially parallel to the longitudinal direction.Advantageously, the fins are arranged in a staggered. According anotheralternative, the fins 23 are corrugated along the longitudinal directionor along the radial direction.

According to another embodiment illustrated in FIGS. 9 and 10, the heatexchanger is equipped with a cover 40 with an aerodynamic profile whichis arranged radially outside the panel 28. Identical elements of thepreceding embodiments are represented by the same numerical references.In other words, the panel 28 is located along the radial directionbetween the fins 23 and the cover 40. Such a configuration allowsfurther to improve the aerodynamics of the heat exchanger and does notdisturb the air flow by the integration of the heat exchanger. As can beseen in particular in FIG. 9, the cover 40 has an outer peripheralsurface 41 having a surface continuity with radially outer surfaces 42,43 of the first and second profiled walls 25, 26.

In particular, the cover 40 has a first portion 44 and a second portion45 which is arranged upstream of the first portion 44 along thedirection of the flow of the air flow in the heat exchanger. The firstportion 44 is defined in a plane having an inclination with respect tothe longitudinal direction L. The inclined plane forms a predeterminedangle beta (β) (see FIG. 10) with a plane (parallel to the plane LT) inwhich the radially outer surface 24 of the support wall 22 is defined.As for the second portion 45, it has a curvilinear shape in the planeRL. The curvilinear portion is here concave. This one is about a quartercircle. Its radius of curvature depends on the length of the panel 28(along the longitudinal direction L). The ratio between the length andthe radius of curvature is between 0.5 and 1.5 mm. The width of thecover 40 is approximately the same as that of the profiled panel. Thecover with its aerodynamic profile allows the heat exchanger to bebetter integrated into the air flow, in particular the secondary airflow, without disturbing it, while the panel 28 here internal improvesthe aerothermal performance of the flow of the air flow inside the heatexchanger. Each cover 40 and panel 28 is optimised for a part of the airflow.

The panel 28 and the cover 40 may be made in one piece (monobloc) so asto simplify the manufacture and the assembly of the heat exchanger. Theadditive manufacturing is a manufacturing method that allow to achievethis goal. It may be provided that the fins 23 are also manufactured inone piece with the panel and the cover and following the samemanufacturing method.

FIG. 11 illustrates yet another embodiment of a heat exchange systemwith a heat exchanger 21 comprising fins 230 which have differentheights. In particular, the fins extend from the radially outer surface24 of the support wall 22 and are covered by a cover 40 having anaerodynamic profile to improve the aerodynamics of the air flow whichbypass the heat exchanger. The cover 40 comprises upstream a first wall25 with a divergent profile and a second wall 26 with a convergentprofile. As in the previous cases, the air flow F2 is slowed down whenentering the air flow and is accelerated when exiting the heat exchanger21. The outer peripheral surface 41 has a surface continuity withradially outer surfaces 42, 43 of the first and second walls 25, 26. Inthe present example, the fins 230 conform to the shape of the cover 40which covers them. In fact, the cover 40 comprises a first inclinedportion 44 and a second curvilinear portion 45. In this way, the fins230 respectively have a height that varies in an increasing and thendecreasing manner from the upstream (of the first wall 25) to thedownstream (of the second wall 26) depending on the flow direction ofthe flow in the heat exchanger. The height of the fins increases up tothe longitudinal junction J between the first inclined portion 44 andthe second curvilinear portion 45. The height decreases from thejunction J. Therefore, there is no panel 28 radially between the finsand the cover.

The fins shown in FIG. 11 are discontinuous and arranged in a staggeredmanner, but they could each extend along the profile of the cover alongthe longitudinal direction and have the radial height varying to conformthe cover. The fins shown, located at the J-junction, have a radiallyouter curved (concave) or substantially shaped like an inverted V end.The fins could also be corrugated along the longitudinal direction andalong the radial direction.

According to another embodiment schematically illustrated in FIGS. 12and 13, the heat exchanger comprises fins 230 which extend radially fromthe support wall 22 and which are covered by a cover 40. The covercomprises a first upstream wall portion and a second downstream wallportion. The fins 230, as in the embodiment shown in FIG. 11, follow theprofile of the cover 40 with an increasing and then decreasing heightfrom upstream to downstream. In particular, with reference to FIG. 13,the fins 230 are continuous and straight along the longitudinaldirection. We also see that there are two types of fin shapes in thisembodiment, a first type of fins supporting the cover and a second typeof fins that does not support the cover.

The first type of fins 230 a comprises a leading edge BA1 and a trailingedge BF1 that extend to the cover. The leading and trailing edges BA1,BF1 have a radially inner end integral with the support wall 22 and aradially outer end integral with the cover. These leading edges BA1 andBF1 are connected by a first surface 231, a second surface 232 and athird surface 233. These surfaces are radially opposite the radiallyouter surface 24 of the support wall 22. The first surface 213 and thethird surface 233 are inclined to a plane parallel to the plane LT andthe second surface extends in a plane substantially parallel to theplane LT.

The second type of fins 230 b comprises a leading edge BA2 and atrailing edge BF2 whose respective heights measured between the radiallyinner end and the radially outer end are less than the height of theleading and trailing edges of the first type of fins 230 a. The leadingand trailing edges BA2, BF2 are inclined respectively and grow from thesupport wall 22 to a height corresponding to that of the second surface232 of the first type of fins.

Each fin has a central portion with a second surface 232 at the sameradial height. We understand that all the fins (or at least the fins ofthe first type 230 a) are connected to the cover at the level of theircentral portion.

In this embodiment, the fins are arranged along the transverse directionso that there is a first type of fins on three fins. In other words, twofins of the second type are arranged adjacent to and between two fins ofthe first type. Of course, the arrangement can be different, for exampleso that every fifth fin is a fin of the first type.

The first and second types of fins allow a heat transfer.

FIGS. 14 to 17 show embodiments of a heat exchanger buried in an annularwall here of a secondary vein V2 of the turbomachine and guiding atleast partly the secondary air flow. The heat exchanger 21 in itsarrangement is swept and/or traversed by the secondary air flow of theturbomachine. The secondary vein is delimited by a radially innerannular wall 50 and a radially outer annular wall 51. The latter iscarried at least partly by the fan casing 11.

According to an embodiment in FIG. 14, the radially outer annular wall51 comprises an opening 510 in which the heat exchanger is installed. Inthis case, the heat exchanger 21 comprises the fins which are covered,on the one hand, by the panel 28 and, on the other hand, by the supportwall 22 (along the radial axis of the turbomachine). The heat exchanger21 also comprises the first profiled wall 25 which is connected upstreamto a portion of the radially outer wall 51 and also to the panel 28, andthe second wall 26 which is connected downstream to a portion of theradially outer wall 51 and also to the panel 28. The panel 28 is offsetradially outwardly from the radially outer wall 51. In this way, thefins 23 are at least partly buried in the wall 51 of the secondary vein,which allows to minimize the disturbance of the flow of the air flow inthe secondary vein. Advantageously, the radially outer wall 51, thefirst wall 25, the panel 28 and the second wall 26 have a continuoussurface. The support wall 22 extends radially away from the radiallyouter wall 51. The wall portion (of the secondary vein with the firstwall 25) forms with the support wall 22 an air inlet having a firstpredetermined height he along the radial axis of the turbomachine whichallows to slow down the flow speed of the air flow at the inlet of theheat exchanger. The wall portion (of the secondary vein with the secondwall 26) forms with the support wall 22 an air outlet hs having a secondpredetermined height hs along the radial axis. The ratio between thefirst height he and the second height hs is between 0.5 and 1.

According to another embodiment in FIG. 13, the radially outer wall 51comprises a step or recess 53 integrating the heat exchanger. The fins23 are thus buried at least partly in the wall 51 of the secondary vein,which allows to minimize the disturbance of the flow of the air flow inthe secondary vein. The fins extend from the recessed wall 52 and areradially covered by a wall 54 as in the embodiment shown in FIGS. 4 to6. The recessed wall 53 forms upstream a fillet 55 a or a first curvedwall that connects the radially outer wall 51 of the secondary vein anddownstream a fillet 55 b or a second curved wall that connects theradially outer wall 51 of the secondary vein. We consider that the panel28 and the first and second walls 25, 26 of the preceding embodiments tobe formed by the recessed wall 53, the curved walls 55 a, 55 b, and thewall portions 51 a, 51 b of the secondary (substantially cylindrical)vein. The support wall 22 is formed by the plate 54. The plate 54extends into the secondary vein. This has a circular or curved (aroundthe longitudinal axis) shape. The wall portion (of the secondary vein)forms, with the wall 54, an air inlet having a first predeterminedheight he along the radial axis of the turbomachine, which allows toslow down the flow velocity of the air flow at the inlet of the heatexchanger. The wall portion (of the secondary vein) forms with the wall54 an air outlet hs having a second predetermined height hs along theradial axis. The ratio between the first height he and the second heighths is between 0.5 and 1. Of course, the panel 28 may be formed by theplate 54 and the support wall by the recess 53.

In the examples of FIGS. 14 and 15, an oil duct 56 is arranged in therecessed wall 53 (or in the panel 28). A part of the air flow F2entering the secondary vein enters the heat exchanger through the airinlet and passes through the fins 23 before exiting the heat exchangerthrough the air outlet and being accelerated. Another part F1 of the airflow flows outside the heat exchanger and along an outer surface of thewall 22, 54. The air flow that circulates outside does not encounter anyobstacles.

The embodiment shown in FIG. 16 differs from the previous embodiments ofFIGS. 14 and 15 in that the oil duct 56 is arranged in the wall 28, 54which extends into the secondary vein. The air flow circulates on bothsides of the oil duct 56 (i.e., inside the heat exchanger and outsidethe heat exchanger), thereby allowing to improve the heat exchangebetween the oil and the air.

In FIG. 17, the embodiment shown differs from the embodiments of FIGS.12 to 14 in that a first oil duct 30 is arranged in the wall 22, 54extending into the secondary vein and a second oil duct 32 is arrangedin the portion of the radially outer wall which carries the fins. Theoil circulating in the first duct 30 exchanges on one side with the airflow passing through the fins 23 and on the other side with the air flowbypassing the fins 23 (which circulates outside the heat exchanger andinto the secondary vein V2).

The buried heat exchanger of FIGS. 14 to 17 may also comprise a cover 40with an aerodynamic profile.

1. A heat exchange system of a turbomachine the heat exchange systemcomprising: a heat exchanger comprising a support wall, a plurality offins each extending in a radial direction from a radially outer surfaceof the support wall and configured to be swept by an air flow, and acover covering the fins, wherein the cover is connected upstream, in adirection of flow of the air flow, to a first profiled wall anddownstream to a second profiled wall, wherein the first profiled wall isarranged upstream from the plurality of fins and configured to guide andslow down the air flow entering the heat exchanger through the pluralityof fins, wherein the second profiled wall is arranged downstream of theplurality of fins and configured to accelerate the air flow exiting theheat exchanger, wherein the cover has an at least partly curvilinearaerodynamic profile and an outer peripheral surface having surfacecontinuity with radially outer surfaces of the first and second walls.2. The heat exchange system according to claim 1, wherein each of thefirst and second profiled wall is attached to the support wall viasupport elements extending radially from the radially outer surface. 3.The heat exchange system according to claim 1, wherein the firstprofiled wall comprises a first wall portion forming, with the supportwall, an air inlet having a first radial height, and the second profiledwall comprises a first wall portion forming, with the support wall, anair outlet having a second radial height, wherein a ratio between thefirst radial height and the second height is between 0.5 and 1,inclusive.
 4. The heat exchange system according to claim 1, wherein thecover comprises a first wall portion defined in an inclined planeforming a predetermined angle with a plane in which the radially outersurface is defined and a second wall portion which is curvilinear andarranged upstream of the first portion.
 5. The heat exchange systemaccording to claim 1, wherein the plurality of fins are continuous andrectilinear each along a longitudinal direction, or discontinuous andstaggered, or are corrugated.
 6. The heat exchange system according toclaim 1, wherein the heat exchanger comprises a profiled panel coveringthe plurality of fins, wherein the profiled panel is substantially flatand extends radially between the plurality of fins and the cover.
 7. Theheat exchange system according to claim 5, wherein the profiled panelextends to a maximum radial distance from the radially outer surfacewhich is greater than the first height and the second heightrespectively of the first and second profiled walls.
 8. The heatexchange system according to claim 7, further comprising a fluidcirculation circuit in which a fluid configured to at least one of coolor lubricate members and/or equipment of the turbomachine circulates,wherein the fluid circulation circuit includes a first duct arranged inthe support wall and a second duct arranged in the panel.
 9. The heatexchange system according to claim 8, wherein the fluid circulationcircuit comprises two channels connecting the first and second ducts toeach other.
 10. The heat exchange system according to claim 1, whereinat least one fin has a different height along the radial direction andwhich varies so as to conform to a profile of the cover.
 11. The heatexchange system according to claim 1, wherein the plurality of finscomprises a first type of fins and a second type of fins arranged on theradially outer surface along a transverse direction perpendicular to theradial direction, the fins of the first type of fins each extendingradially between the support wall and the cover, and each being attachedto the cover so as to bear the cover over their full radial heights. 12.The heat exchange system according to claim 11, wherein the plurality offins is arranged transversely so that every third fin is a fin of thefirst type.
 13. The heat exchange system according to claim 1, whereinthe heat exchanger is an additively manufactured heat exchanger.
 14. Amodule of a turbomachine with a longitudinal axis, comprising: anannular casing around the longitudinal axis in which an air flowcirculates and a heat exchange system according to claim 6, wherein theheat exchange system is arranged in the annular casing, wherein theannular casing comprises an annular wall which guides at least partlythe air flow and which has an opening or a recess in which the heatexchanger with the profiled panel is installed, the first wall beingconnected upstream of the panel to a portion of the annular wall and thesecond wall being connected downstream of the panel, to a portion of theannular wall.
 15. A turbomachine comprising at least one heat exchangesystem according to claim
 1. 16. A turbomachine comprising at least oneturbomachine module according to claim 14.